U.S. Pat. Nos. 2,540,194 and 5,225,731 each disclose piezoelectric actuators of the above mentioned general type. Namely, the known actuators comprise a one-piece integral piezoelectric solid state body that has stripe-shaped electrodes applied on opposite outer surfaces thereof, whereby the electrodes are spaced apart from each other in the lengthwise direction of the solid state body, and respective paired electrodes positioned opposite each other are electrically connected to each other. Adjacent electrodes in the lengthwise direction are alternately energizable with opposite voltages. This arrangement creates a plurality of virtual piezoelectric layers having layer thicknesses corresponding to the electrode spacing. The piezoelectrically induced strain in the piezoelectric layers is summed or added together along the lengthwise direction of the solid state body.
The above described known actuators are intended to be simpler than other prior art actuators, in view of the monolithic structure of the solid state body. However, in order to achieve a sufficiently homogenous electric field line pattern, the solid state body must have a rather small plate thickness and is therefore correspondingly sensitive to breakage. Furthermore, the contact arrangement necessary for energizing the electrodes is rather complicated because a double electrode connection is necessary at the end of each piezoelectric layer. Thus, the complexity of i-he overall contact arrangement and the effort involved in assembling the known piezoelectric actuators is quite considerable, especially if a large number of piezoelectric layers is to be used in order to achieve an advantageous amplification or summation of the piezoelectric effect.